Abstract

The radiated power emanating from a bent single-mode fiber is computed for various radii of curvature by a full-vectorial analysis. The only approximation is the truncation of a spectral series, the accuracy of which can be controlled. Hence, the complex propagation coefficient of the fundamental mode approaches the exact value and consequently, the bending loss does as well. Two widely accepted bending-loss formulas, based on asymptotic approximations to scalar-field theory, are compared with our full-vectorial results. Both have a limited region of validity. For simplicity, the comparison is performed on a step-index fiber with a cladding of infinite extent. However, the full-wave method is capable of dealing with arbitrary index profiles.

Figures (5)

(a) Bent fiber in a toroidal coordinate system (state B). The surface ∂D separates the interior (shaded) from the exterior region. (b) Ring sources placed on an imaginary torus within the interior region and situated in a homogeneous medium (state A).

(a) Bending losses in a step-index fiber as a function of the radius of curvature. The approximations of Eq. (5) and Eq. (6) are set against the full-vectorial results. (b) The location of the propagation coefficient ν in the complex plane. The solid disc indicates the result for R=4mm.